The present invention pertains to a conveying device for vertically transporting piece goods.
Two respective inner and outer conveying means endlessly circulate on partially congruent paths and are synchronously driven. The paths of the inner and outer conveying means are spaced apart from one another in an essentially vertical strand. Several platforms are coupled to the conveying means and essentially lie horizontally in the vertical strand. The piece goods are fed to the platforms horizontally by a first conveyor and the platforms deliver the piece goods horizontally to a second conveyor, situated forward of and at a different elevation than the first conveyor.
Conveying devices of this type are also referred to as vertical circulating elevators, elevators or rack conveyors and disclosed in DE 11 71 814 B and DE 38 33 750 A1. As described in the aforementioned documents, they may be realized in the form of S-conveyors, in which the delivery direction is identical to the feed direction, or in the form of C-conveyors, in which the piece goods are delivered opposite to the feed direction, as illustrated and described in DE 195 30 288 A1. The piece goods can be transported upward or downward with these conveying devices.
In such conveying devices, link chains are used as inner and outer conveying means while an elevator with a toothed belt is illustrated and described in DE 39 15 074 A1. The deflecting elements in the paths of the inner and outer conveying means consist of deflection pulleys. The inner and outer conveying means are continuously driven with a constant transport speed by means of a common drive shaft.
Due to the deflection from the horizontal transport direction into the vertical transport direction and vice versa, the platforms need to be mutually spaced apart by a distance that must be greater than the platform length plus the maximum piece good height to be transported in order to enable the platforms with the piece goods lying thereon to circulate in a collision-free fashion. This requires a relatively large cycle spacing in the supplied stream of products with correspondingly faster transport speeds in the conveying device and on the upstream and downstream transport systems.
Another disadvantage of known conveying devices can be seen in that the arc-shaped deflection into and out of the vertical strand and the centrifugal forces occurring during this deflection limit the transport capacity because the piece goods need to be prevented from shifting on the platforms. Otherwise, a fixed cycle sequence in the stream of products would be lost and the piece goods would have to be realigned relative to one another and rearranged in a cyclic fashion for subsequent processing. In the worst-case scenario, the piece goods would slide off the platforms in the deflecting region and fall into the conveying device. Piece goods that are transported in a stacked fashion would fall apart or lose their alignment relative to one another. Shifting piece goods on the platforms may also lead to markings on sensitive surfaces, for example, on books or similar printed products. The described deficiencies can be observed, in particular, in the upper deflecting region. At this location, it may even occur that the piece goods are lifted off the platforms at an excessively high speed.